Active reabsorption of alveolar sodium and fluid by the epithelium is critical in resolution of pulmonary edema with lung injury. This is accomplished by coordinated action of the sodium channel and sodium pump, Na,K-ATPase. Oxidants are a pathophysiologic mechanism of lung injury and hyperoxia is a model for acute lung injury. In the current funding period, we systematically defined the impact of hyperoxia on the levels of Na,K- ATPase mRNA, protein and function in three models. We found: increased gene expression; differential effects on the alpha1 and beta1 subunit levels and synthesis rates with preservation of the beta1 subunit; inhibition of the sodium pump Vmax, but stable steady state activity in intact type II cells; and a heterologous response of rats in vivo in their active alveolar sodium resorption. Now we will target the mechanisms underlying these observations in three aims. Aim 1 use type II cell monolayers to dissect the ion transport mechanisms affected by hyperoxia and stimulated by beta-adrenergic agonists. In Aim 2, we will determine whether Na,K-ATPase is oxidized and the functional consequences of oxidation. We also will assess translational regulation of the sodium pump and which mRNA and protein isoforms are expressed in human and rat lungs after injury. Finally, Aim 3 uses a transgenic mouse sodium pump promoter- reporter model to assess the in vivo triggers for Na,K-ATPase gene up- regulation. The results of these studies should help us design well founded strategies for up-regulation of fluid resorption that can be tested in preclinical models and human clinical trials.